Background: Study aimed at assessing the impact of elevated fluoride from drinking water on thyroid gland structure and function in fluorosis prone areas. Iodine is incorporated in the thyroid synthesis by thyroid gland but in the presence of low Iodine levels fluoride is likely to interfere with the concentrating capacity of thyroid of iodine in thyroid production, consequently reflecting changes in thyroid parameters and also cytomorphological features manifesting hypothyroidism in association with different pathological entities.Methods: Prakasam district in Andhra Pradesh is fluorosis prone zone and subjects are picked up from highly vulnerable zone in this district and their specimens are collected to study cytomorphological changes of the thyroid gland and biochemical parameters of blood samples for thyroid function test were considered. Cytological study by way of Fine Needle Aspiration Cytology (FNAC) of thyroid gland, biochemical parameters pertaining to function of thyroid gland namely Free triiodothyronine (FT3), Free Thyroxine (FT4) and Thyroid stimulating hormone (TSH) were assessed in the subjects from fluorosis prone zone.Results: The results were statistically significant with concurrent association of different cytological alterations of thyroid gland in these subjects like Hashimoto’s thyroiditis of hypothyroidism, adenomatous goitre, colloid goitre and few of follicular adenoma/neoplasm. FNAC makes cytological changes evident showing different morphological features that comprise different pathological entities largely with an evidence of hypothyroidism in most of the cases in the given study.Conclusions: The results of the study strongly suggest assessing the magnitude of the problem of fluorosis and also magnitude of its influence on thyroid structure and function that warrants assessment of the thyroid function by biochemical and cytological studies.

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Study aimed at assessing the thyroid function under the influence of high fluoride content in the water in fluorosis prevalent zones. In addition to bone and teeth soft tissue like thyroid gland were also shown to be affected as evident from the earlier studies. Fluoride can rapidly cross cell membrane in tissues that are metabolically active and hence the thyroid gland. Fluoride also interferes with Thyroid Stimulating Hormone (TSH) production and also the thyroid hormones free Triiodothyronine (FT 3 ) and free Thyroxine (FT 4 ). Prakasam district in Andhra Pradesh is fluorosis prone zone and subjects visiting Government medical institution from these areas are chosen as subjects and blood samples were collected to study parameters of thyroid function tests [FT 3 , FT 4 and TSH]. Fluoride levels of the water from the fluorotic zones and also in the serum of the subjects were estimated for the correlative study. Altered thyroid function was evident with low FT 3 , FT 4 levels and high TSH levels. Concurrently high levels of fluoride were seen in the water samples from the concerned areas, the subjects hailing from. The results were statistically significant reflecting hypothyroid status in majority of the subjects in association with fluorosis as evident by high levels of fluoride in the water.